Manufacture of alkyllead compounds with calcium-lead alloys



Patented Apr. 22, 1952 MANUFACTURE -or ALKYLLEAD M- POUNDS WITH CALCIUM-LEAD ALLOYS Hymin Shapiro, Detroit, and Ivar T. Krohn, Royal Oak, Mich., assignors to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application May 29, 1951, Serial No. 229,002

3 Claims. (Cl. 260437) This invention relates to a new process for making alkyl-lead compounds.

Among the objects of our invention is to provide a process in which a substantial yield of tetraethyllead is obtained for a definite range in composition for a calcium-lead alloy.

The above object is accomplished by reacting an alkylating agent with a particular calciumlead alloy composition. We have found that not all calcium alloys of lead are reactive. For instance, we have found that no alkyllead is formed from an alloy composition having an atom ratio of calcium to lead of 2 to 1 which corresponds to the formula CazPb. This alloy is unreactive although from a theoretical viewpoint it is the most desirable alloy since no free lead would be formed according to the following reaction:

in which R is an alkyl radical.

Further, when the atom ratio of calcium to lead exceeds about 3.5 to 1, no yield is obtained. However, we have made the unexpected and surprising discovery that substantial yields of alkyllead products are obtained when alkylating a calcium-lead alloy in which the atom ratio of calcium to lead is between about 2.2 to 3.5 to 1.

Any of the alkylating agents heretofore used or described in the prior art can be used, among which are the alkyl halides preferably the iodides, bromides and chlorides, the dialkyl sulfates and the trialkyl phosphates. In general, the alkylating agents are esters of inorganic acids having the proper alkyl groups for making the desired alkyllead compound, and having an inorganic acid group which forms a salt with calcium. Among those which can be used in our invention are the ethyl, propyl and butyl chlorides, as well as the corresponding bromides and iodides, diethylsulfate and triethylphosphate.

While tetraethyllead is the principal compound discussed herein because of its large commercial use, other alkyllead compounds such as tetramethyllead, tetrapropyllead, dimethyldiethyllead and methyltriethyllead can be made by the process of our invention.

The temperature employed is not important, the preferable range being 50 and 100 C. The pressure used is not critical but should be sufiicient at the temperature employed to maintain the alkylating agent in the liquid phase. The time of reaction is between about 30 minutes and 8 hours. The amount of alkylating agent employed is not critical but an excess over the stoichiometric amount required is preferred.

Our invention can be best understood by referring to the following t'ypicalworking examples in which all the parts are by weight and the percentages are by weight based on the lead charged.

. Example I A charge of 100 parts of calcium-lead alloy having an atomic ratio of calcium to lead of 2.35 to 1 is added to a reaction vessel equipped with an agitator, a jacket for circulation of heating or cooling liquids, a reflux condenser, charging and discharging ports, liquid feed lines, and means for releasing the pressure. Liquid ethyl chloride in the amount of 225 parts is added under pressure to the stirred solids in the vessel over a period of one-half hour. By controlling the flow of liquid in the autoclave jacket and in the reflux condenser the temperature of the reaction mass is permitted to rise from an initial temperature of 50 C. to a temperature of 85 C. during this feed period. The pressure in the autoclave during this feed rises to '75 pounds per square inch gauge where it is maintained. The temperature of the stirred reaction mixture is maintained at C. for about 5 hours at the end of which the pressure is reduced to atmospheric and the reaction mass removed and charged to the steam still wherein the alkyllead product is recovered. The yield of tetraethyllead is 9.8 parts or 9.2 per cent based on the lead present in the calcium-lead alloy.

In another example in which the conditions were the same except that the atomic ratio of calcium to lead was approximately 2 to 1, the yield of tetraethyllead was 0. Thus, when the atomic ratio of calcium to lead is less than that of our invention little or no tetraethyllead is obtained. Likewise, when the atomic ratio of calcium to lead was increased over that of our invention no yield is obtained. For example, when the atomic ratio of calcium to lead was increased to 3.73, keeping all the conditions the same as those given in Example I, no tetraethyllead was obtained.

On the other hand, when following the procedure of Example I, except that the atomic ratio of calcium to lead was changed to 2.51 in one case and 3.4 in another case, substantially the same yields as those given in Example I are obtained.

The above examples show that the atomic ratio of calcium to lead is critical and that if it is varied substantially from the range given herein, little or no yields are obtained.

The above examples employed ethyl chloride as the alkylating agent. However, other alkyl halides such as the bromides and iodides gave substantially the same results.

Thus, a substantial yield of tetraethyllead is made by our process when using alloys within the atomic .ratio of calcium to .lead of between about 2.2 .to 1 and 3.5 to 1 whereas no yieldis obtained when the composition varies substantially therefrom.

Furthermore certain catalysts of the carbonyl type substantially improve the *results obtained. Among such catalysts are theke'tones, alde'hyde's, acid anhydrides, esters andiother *derivatives of 'carboxylic acids.

Other embodiments of our invention oan be made without departing from the spirit andscope of our invention which is not limited"to5fl6"ific embodiments given herein.

We claim:

1. The process for making hydrocarbon-lead compounds comprising reacting a calcium-lead alloy consisting essentiallyof analloy having an ,ethyllead in which the alkylatingvagent is an ethylating agent. 3. The process of claim 1 for making tetraeth- .yllead in which the alkylating agent is ethyl chlo- -'ride.

HYMIN SHAPIRO. V IVAR T. KROHN.

REFERENCES CITED The following references are of record in the ifi le of this patent:

UNITED STATES PATENTS Number Name 7 Date 1,500,954 Mathesius et al July 8, 1924 2,535,237 Shapiro Dea -26, 1950 

1. THE PROCESS FOR MAKING HYDROCARBON-LEAD COMPOUNDS COMPRISING REACTING A CALCIUM-LEAD ALLOY CONSISTING ESSENTIALLY OF AN ALLOY HAVING AN ATOMIC RATIO OF CALCIUM TO LEAD OF BETWEEN ABOUT 2.2 TO 1 AND 3.5 TO 1 WITH AN ALKYLATING AGENT WHICH INCLUDES THE HYDROCARBON RADICAL IN QUESTION AND HAVING A NEGATIVE RADICAL WHICH REACTS WITH CALCIUM. 